文摘
Titanium dioxide (TiO2) displays photocatalytic behavior under near-ultraviolet (UV) illumination.In another scientific field, it is well understood that the excitation of localized plasmon polaritons on thesurface of silver (Ag) nanoparticles (NPs) causes a tremendous increase of the near-field amplitude atwell-defined wavelengths in the near UV. The exact resonance wavelength depends on the shape and thedielectric environment of the NPs. We expected that the photocatalytic behavior of TiO2 would be greatlyboosted if it gets assisted by the enhanced near-field amplitudes of localized surface plasmon (LSP). Herewe show that this is true indeed. We named this new phenomenon "plasmonic photocatalysis". The key toenable plasmonic photocatalysis is to deposit TiO2 on a NP comprising an Ag core covered with a silica(SiO2) shell to prevent oxidation of Ag by direct contact with TiO2. The most appropriate diameter for AgNPs and thickness for the SiO2 shell giving rise to LSP in the near UV were estimated from Mie scatteringtheory. Upon implementing a device that took these design considerations into account, the measuredphotocatalytic activity under near UV illumination of such a plasmonic photocatalyst, monitored bydecomposition of methylene blue, was enhanced by a factor of 7. The enhancement of the photocatalyticactivity increases with a decreased thickness of the SiO2 shell. The plasmonic photocatalysis will be of useas a high performance photocatalyst in nearly all current applications but will be of particular importancefor applications in locations of minimal light exposure.